1. Field of the Invention
This invention relates to devices used to control the flow of fluids containing solid particles and other harsh contaminants, such as process slurries used in coal gasification and liquefaction. More specifically, it relates to the use of pairs of opposing jets originating from nozzles for pressure letdown and flowrate variation of erosive fluids.
2. Prior Art
Present technology for flow control and pressure letdown of fluids containing erosive solids utilizes throttle valves of various kinds such a conventional globe valves angle valves, and plug-and-seat valves. Conventional globe valves have abrupt changes in flow direction through the valve body and around the plug/seat which particles in the stream cannot follow and so impinge on solid surfaces in the valve cauisng severe erosion. In the Willis angle valve rotating and stationary disks with one or more holes are used, with flow throttling achieved by the angle of rotation of the rotating disk, e.g., 0.degree. being fully closed and 90.degree. fully open. Here particle impingement causes erosion of both disks. Like the angle valve plug-and-seat valves(Cameron Kieley-Muller) have no abrupt changes in flow direction, but all the same both plug and seat suffer erosion regardless of the design of the countour of the variable area due to plug motion.
The erosion of throttle valves by solids in the flow leads to associated problems such as:
1. Short valve lifetime due to rapid erosion/corrosion of valve body and trim;
2. Loss of flow control due to erosion, structural failure of trim elements and accumulat1on of and plugging by solids in the stream;
3. High safety hazard due to increased risk of structural failure from erosion; and
4. High cost of valves due to need for expensive, scarce, refractory trim materials (stellite, tungsten carbide) to achieve present technology "short" operating lifetimes.